There is no code. But... you should visit arcadeprehacks.com! it
has free hacked games. If you play Thing Thing Arena 3... you get
FULL HEALTH , FULL AMMO , AND ALL WEAPONS!
View page
There aren't really any cheat codes for Thing Thing Arena 2.
There are small hints that can help you through the game, but the
game has not cheat codes that you can enter or cheats you can
perform.